1. Field of the Invention
The present invention relates to a junction structure for a flat cable.
2. Description of the Related Art
Flat cables, in which a plurality of electrical conductors are arranged parallel and are covered with an insulating material, are used for wiring on apparatuses which have moving parts. In a roll connector for a steering system of an automobile, for example, a flat cable is loosely stored in a coil shape in a connector case.
Usually, a lead wire is attached to the flat cable for connecting the roll connector to an external apparatus. The cable and the wire are connected by the following methods.
In the first known connecting method, the flat cable and the lead wire are first positioned by means of a jig for aligning electrical conductors of the lead wire with the conductor pitch of the flat cable, before assembling the roll connector. Then, the counterpart conductors are connected respectively by welding or the like, and a cover of plastics or other material is set onto each junction. Thereafter, the flat cable, with the lead wire connected thereto, is housed in the connector case to assemble the roll connector, with the lead wire drawn out of the connector case through an outlet formed in the case. After the roll connector is assembled in this manner, a connector is attached to the other end of the lead wire.
In the second known connecting method, on the other hand, after the roll connector is assembled into a flat cable, having connection conductors at one end thereof, contained in the connector case, the end portion of the flat cable is drawn out through the outlet of the connector case. Then, an insulating material is removed from one end of the lead wire, the other end of which is connected with the connector in advance, whereby the conductors are exposed. The flat cable and the lead wire are fixed at the outlet by means of the positioning jig, the counterpart electrical conductors are connected respectively by welding or clamping, and a cover is then put on the outlet portion.
In either of said known connecting methods, which require a special jig for positioning a flat cable and a lead wire, the efficiency of the connecting operation is rather low. Particularly in the second known connecting method, the flat cable and the lead wire are connected at the outlet of the connector case, so that the jig must be shaped to be matched with the outlet portion. This is costly. Since the cable and the wire have to be connected at the outlet portion, the connecting operation is very difficult.
When welding the flat cable and the lead wire, the conductors are susceptible to misalignment, and the welding operation is difficult, thereby lowering the welding accuracy and the resultant tensile strength despite the use of a positioning jig. Thus, there has been a demand for an improvement of the junction structure of the flat cable.